1. Field of the Invention
The present invention relates to the conversion of chemical energy to electrical energy. More particularly, the present invention relates to a conductive substrate providing enhanced contact with an electrode active material. The improvement in electrode active contact is provided by chemically machining selected portions of the opposed major surfaces of the conductive substrate. The thusly fabricated substrate is particularly useful as a current collector in an electrochemical cell.
2. Prior Art
Presently, there are many different techniques for fabricating current collectors including subjecting a conductive foil substrate to mechanical expansion and perforating a conductive foil. However, mechanically expanded metal screens and perforated foils often have burrs which are potential contributors to battery shorting. Other typical state-of-the-art current collector designs, such as conventional chemical machining (etching or milling), electrolytic etching, and conductive foils provided with a vapor deposited bonding layer, attempt to increase the contact surface area without altering the generally planar configuration of the substrate workpiece. Maintaining the substrate having a planar surface structure limits the degree to which the contact surface area can be increased. In that respect, foil screen designs limit the variety of active material that can be contacted thereto. For example, adherence of pressed powders or flexible sheets of electrode active material to foil screens is virtually impossible. Finally, conventional woven fabric collectors are limited to minimum thicknesses required to maintain structural integrity. This detracts from improvements in reducing the passive volume of the fabric.